Harris County poised to receive grant to study flood tunnel idea

Water is released from the Barker Reservoir in the aftermath of Tropical Storm Harvey on Tuesday, Aug. 29, 2017, in Houston. ( Brett Coomer / Houston Chronicle )

Water is released from the Barker Reservoir in the aftermath of Tropical Storm Harvey on Tuesday, Aug. 29, 2017, in Houston. ( Brett Coomer / Houston Chronicle )

Photo: Brett Coomer, Staff / Houston Chronicle

Photo: Brett Coomer, Staff / Houston Chronicle

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Water is released from the Barker Reservoir in the aftermath of Tropical Storm Harvey on Tuesday, Aug. 29, 2017, in Houston. ( Brett Coomer / Houston Chronicle )

Water is released from the Barker Reservoir in the aftermath of Tropical Storm Harvey on Tuesday, Aug. 29, 2017, in Houston. ( Brett Coomer / Houston Chronicle )

Photo: Brett Coomer, Staff / Houston Chronicle

Harris County poised to receive grant to study flood tunnel idea

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The Harris County Flood Control District is set to receive a $320,000 federal grant to study the feasibility of constructing deep underground tunnels to move stormwater to the Houston Ship Channel without overburdening the area’s bayous.

The grant, from the U.S. Economic Development Administration, will fund a four-month investigation to determine whether such tunnels would be a practical and cost-effective addition to the county’s long-term flood protection strategy. The flood control district has begun work on scores of projects funded by the $2.5 billion flood bond approved last summer, though none to date include underground tunnels.

“The study is basically to look at our ground conditions, including our groundwater table, and compare that to existing technology in the tunnel industry to see if there’s a match,” said Russ Poppe, executive director of the flood control district. “If that’s true, then we can start looking at costs, routes and opportunities we can potentially pursue.”

Engineers envision a system in which tunnels at least 20 feet wide and 150 feet deep use gravity to move water from upstream bayous to the ship channel, in some cases a distance of 30 miles. The region’s flatness, in some areas less than one foot of elevation change per mile, presents a significant obstacle.

San Antonio, Dallas and Austin have built stormwater tunnels, though the soft soils and high water table in the Houston region are unique challenges. Poppe said Washington, D.C, a similarly low-lying city, recently completed a tunnel system beneath the Anacostia River.

District leaders are quick to assert no single mitigation system can cure Houston of its flooding woes, which have damaged property and frustrated residents since the city was founded. They say tunnels could, however, help Harris County achieve protection against 100-year floods, which have a 1 percent change of occurring any given year.

“People are getting really excited about it,” Poppe said. “We’re hopeful this can be a new tool in our toolbox.”

Jim Blackburn, co-director of the Severe Storm Prediction, Education, and Evacuation from Disasters Center at Rice University, raised no objection to studying the tunnel idea but said he worries that pursuing the proposal could become a boondoggle that siphons money from other, more urgent priorities.

“It’s one of those big dream projects that may take us away from much more reasonable short-term projects,” Blackburn said. “I doubt the feasibility of it.”

The flood control district said tunnels could cost anywhere from $40 million to $163 million per mile, and county officials last year estimated a total price tag of several billion dollars. In 1996, the flood control district published a report that included a proposal to build a tunnel beneath the Katy Freeway to channel water 12 miles east. County officials took no action on the idea.

Poppe said tunneling in heavily developed areas may be less expensive than widening bayous, which would require the county to purchase additional rights of way. He said boring channels beneath bayous with natural banks, like Cypress Creek in northern Harris County, may be less disruptive to ecosystems than channeling the waterways with concrete.

Commissioners Court may sign off on the study, which would also include $80,000 in local matching dollars, as early as Feb. 26.

The research is part of the district’s 2018 flood bond program, which voters approved this past August. The program, which likely will include more than $2 billion in matching federal dollars, is the single largest flood control investment in Harris County history and also includes $20 million for engineers to design a tunnel system.

Engineers plan to complete more than 230 flood protection projects and studies, including a report on whether to build a third reservoir in west Houston.